The present invention relates to a device for changing the status of a dual status magnetic electronic article surveillance marker.
Magnetic electronic article surveillance (xe2x80x9cEASxe2x80x9d) markers have been used for many years to protect items of value against theft. These EAS markers typically have a signal-producing layer made of a low coercive force, high permeability magnetic material, and a continuous or segmented signal-blocking layer made of a permanently magnetizable magnetic material. When the signal-blocking layer is activated, it effectively prevents the signal-producing layer from providing a signal that is detectable by an EAS detection system, and thus the EAS marker is deactivated. When the signal-blocking layer is deactivated, then the EAS marker is activated, and an EAS detection system is able to detect the marker. EAS markers that may be activated and deactivated as described are sometimes referred to as xe2x80x9cdual-statusxe2x80x9d markers, to distinguish them from xe2x80x9csingle-statusxe2x80x9d markers that are always activated. Billions of dual-status EAS markers have been sold to date, and they protect assets such as library materials against theft around the world.
The devices used to activate and deactivate magnetic EAS markers are themselves magnetic. That is, they may include an array of magnets or an electric coil that produces a magnetic field of a desired intensity near a working surface, so that the EAS markers may be passed over that surface to selectively activate or deactivate the marker. Unfortunately, some devices used to change the status of a dual-status marker have the potential to harm magnetically-recorded media, such as videotapes. That is, magnetically-recorded media can be erased, garbled, or damaged by the presence of a magnetic field. Thus, when magnetically-recorded media are passed over a device to change the status of an EAS marker attached thereto, the device may damage the magnetically-recorded media. In view of the foregoing, it is desirable to provide a device for deactivating dual-status magnetic EAS markers that will not damage magnetically-recorded media such as videotapes.
Conventional activation and deactivation systems may reliably activate or deactivate EAS markers positioned along the spine of a book, for example, because the position and orientation of the marker relative to the magnetic field is generally known. With a compact disc, the EAS marker is likely to be positioned on the disc itself, and accordingly may be at any orientation in the X-Y plane relative to the case in which the disc is contained, and thus relative to the applied magnetic field. For example, when the marker is of the type shown in FIG. 1 of U.S. Pat. No. 5,699,047, which is assigned to the assignee of the present invention, the marker may include two elongated marker elements on a support sheet, such that when the marker elements are affixed to the compact disc, they are symmetrically disposed about the centered circular hole in the compact disc. Because the orientation of the markers in the X-Y plane relative to the case in which the disc is contained is essentially random, the markers can be difficult to reliably activate or deactivate without raising the applied magnetic field to a level at which magnetically-recorded media such as video tapes would be damaged. It would be desirable to provide a device that reliably activates and deactivates such markers, while preserving the ability to reliably activate and deactivate the EAS markers associated with videotapes without damaging those tapes.
A device is provided according to the present invention for changing the status of a dual-status electronic article surveillance marker. The device comprises a coil for creating a magnetic field in a first direction, and a coil for creating a magnetic field in a second direction that is approximately perpendicular to the first direction. The device may include a housing having a passageway therethrough, such that an article to which the marker is attached is positioned within the passageway so that the marker passes through the passageway in an orientation that is generally in the plane defined by the first and second directions. The device may apply the magnetic fields in the first and second directions sequentially or simultaneously, and may even include a coil for creating a magnetic field in a third direction that is substantially perpendicular to the plane defined by the first and second directions. These and other aspects of this invention are described in more detail below.